Moulded case circuit breakers first appeared in the United States as the result of a federal directive to electrical manufactures to develop a circuit pritection device which would be more reliable and convenient than the fuses they were to replace.

Companies such as the westing-house Electric Corporation in Pittsburgh, Pennsylvania and the Heinemann Electric Company in Trenton, New Jersey, successfully took up the challenge and by the early 1930's were peoducing circuit breakers which fulfilled the criteria laid down by this directive.

These companies originally manufactured circuit breakers which utilised the thermal-magnetic operating principle, although Heinemann Electric subsequently developed a circuit breaker which operated on the Magnetic-magnetic principle

The foundations of CBI were established in 1949 as a joint venture by the Heinemann Electric Company in Trenton, New Jersey, USA and operated as Heinemann Electric (S.A.) Limited Another manufacturer, Fuchs Electrical Industries, which held the Westinghouse license form 1953, was acquired in 1986 and merged into a new company called Circuit Breaker Industries Ltd(CBI).

CBI thus continues in hte tradition of the tw pioneers in circuit breaker technology. Whereas the Magnetic-Magnetic technology is traditionally used in the protection of equipment, CBI has adapted this principle og operation for cable protection in residential and industrial installations, as well as for the protection of outdoor reticulation systems of the electricity utilites. For this purpose, the company has buit up an extensive Research and Development capability.

After recovering from a devastating fire in 1986, CBI has continued to grow becoming the largest circuit breaker manufacturing facility of its kind on the African continent.

In the early 1950's, South Africa was amongst the pioneers in establishing a set of standards for circuit breakers outside the USE. Consequently, CBI products have been almost exclusively used in residential and industrial installations in South africa, making this country one of the first to use circuit breakers for electrical protection on a large scale.

Shortly thereafter, the use of earth leakage protection devices for domestic purposes became widespread and it can be confidently said that South African enginerers lead the field in the design and application of earth leakage protection systems. This resulted in south Africa becoming the first country in the world(1976) to residual current devices mandatory in all industrial and residential electrical installations.

As the only local manufacturer of circuit breakers and residual current devices, CBI has achieved international recognition for its competence in this field and continues to represent the South African Bureau of Standards on the technical committees of the International Electrotechnical Commission(IEC), hus being instrumental in the development of international electrical safety standards.